It is often necessary to attach soft tissue to bone, for example, to attach ligament tissue to bone tissue. Loss of integrity in bone tissue, for example, a ligament of a human rotator cuff, as well as recurrent dislocation of the shoulder, may result in abnormal kinematics of the shoulder. This may cause progressive weakness of the shoulder and, in some circumstances, severe dysfunction of the shoulder and progressive degenerative joint changes. Accordingly, procedures have been developed to repair, for example, the rotator cuff, to prevent debilitating loss of function and to restore more physiologic biomechanics. However, these conventional procedures may require invasive surgical procedures, which may lead to increased complications and increased morbidity.
In response, various minimally invasive techniques for reattaching tissue to bone have been developed, such as the techniques referred to in Gartsman, G. M. et. al., “Arthroscopic Repair of Full Thickness Tears of the Rotator Cuff”, J Bone Joint Surg Am 1998; 80:832-840. Many of these techniques describe the use of suture anchors to maintain proximity between soft tissue and bone, thereby facilitating re-attachment of the soft tissue to the bone.
Many of the early suture anchors were operable to be screwed into the bone. However, to properly secure such an anchor, the bone had to be first prepared by a separate tapping step (i.e., a pre-drilling step). In an effort to eliminate the initial tapping step, push-in type anchors were developed. The effectiveness of push-in type anchors may be measured by their ability to reliably set in all bone types, the size of the anchor, and the effectiveness of insertion tools for protecting suture threads while inserting the anchors into bone.
With respect to push-in type suture anchors, the insertion tool, the suture implant, and the method of insertion should act to consistently and reliably set the implant in a variety of bone types. For this purpose, the implant should be designed as small as possible to limit the amount of foreign substance in the body, and should have features configured to consistently set the anchor into bone.
U.S. Pat. No. 5,618,314 to Harwin et al. relates to an anchor with a plurality of wing members fixed distally on the proximal end thereof. As characterized, the wing members are symmetric about the longitudinal axis of the anchor, and configured to be inserted straight into bone. After insertion into bone, the wing members expand outwardly to cause fixation of the anchor to the bone. However, it is believed that such a design may not provide sufficient fixation in soft bone.
U.S. Pat. No. 5,690,676 to Dipoto et al. relates to an anchor having one or more fixed rib members symmetrically arranged around a longitudinal axis of the anchor. As characterized, the anchor is driven into bone by an external force applied to the proximal end of the anchor (i.e., the back of the anchor). Effective insertion of the anchor into the bone requires that the anchor be driven on a ‘straight-line’ trajectory, without a second fixation step (e.g., a rotation step) for positive engagement of the ribs to the bone. In this manner, the anchor requires the elastic action of good bone to spring back into place after passage of the fixed rib members to prevent the anchor from exiting the bone once inserted. However, in soft or poor quality bone, bone elasticity may be negatively affected, which may cause inadequate fixation of the anchor to the bone.
U.S. Pat. No. 5,527,342 to Pietrzak et al. relates to a suture anchor having a rib for fixation to bone. In one embodiment, the rib extends radially from the longitudinal axis to the bone, but is not intended to be toggled into a final locked position. In this manner, it is believed that such a configuration does not effectively fix within bone.
U.S. Pat. Nos. 6,146,407 and 6,165,203 to Krebs relate to ribbed anchors designed to be fixed to bone via a secondary fixation step. These anchors have axially aligned (one or more) ribs, which are inserted into bone and rotated by applying force on the proximal end of the implant. However, it is believed that such an anchor creates too large of a hole in the patient's bone.
U.S. Pat. No. 4,898,156 to Gattuma et al. relates to an implant having a resilient elastic rib attached to a coupling member. As characterized, the elastic rib causes a toggle or rotation of the anchor in the bone upon insertion. However, since the anchor is not configured to be rotated by a secondary fixation step (e.g., a rotation step), it is believed that the effectiveness of such an anchor depends on the quality of bone within which the anchor is inserted.
U.S. Pat. Nos. 5,540,718, 5,782,863, 5,871,503, 5,879,372, 6,146,408, and 6,306,158 to Bartlett relate to methods of causing off axis rotation of a suture anchor within bone. The methods require the use of an insertion tool having an elastic distal end for initiating a toggle of the anchor upon insertion of the anchor into bone. When implanted in good quality bone, the anchor and bone hole interface purportedly impart a frictional force, which causes the elastic tip of the insertion tool to bend, thereby causing the anchor to toggle and fix to the bone. However, it is believed that an insufficient frictional force may be generated if the anchor is inserted into poor quality bone.
Due to the limitations of the conventional suture anchors, delivery instruments, and methods described above, a need exists for a simple, strong, and reliable suture anchor, as well as a technique for fixating suture to bone.
Furthermore, a need exists for a push-in type suture anchor and delivery instrument that protects the sutures during insertion of the anchor into bone.